Synovial cysts of the temporomandibular joint are rare. They commonly occur in the wrist, knee and feet. The main symptoms of synovial cysts occurring in the temporomandibular joint include preauricular pain and swelling, and surgical removal is the gold-standard treatment. A 54-year-old woman who presented with swelling of the right temporomandibular joint visited Kyungpook National University Dental Hospital. She had undergone enhanced computed tomography from another hospital, which showed a 1.1 × 0.8 × 1 cm well-defined rounded cystic lesion on the lateral area of the right temporomandibular joint. A synovial or ganglion cyst was suspected. The cystic lesion was surgically removed under general anesthesia and was histopathologically diagnosed as a synovial cyst. Histopathological findings show a lumen surrounded by loose fibrous tissue, and the lining is in a folded form and is composed of synovial cells.

Synovial cysts are found mainly in periarticular areas of the wrist, ankle, and knee, but also rarely in the temporomandibular joint (TMJ). Only 1 case of bilateral synovial cysts in the region of the TMJ has been reported. This case report described bilateral cysts in the TMJ in a 54-year-old Korean woman. T2-weighted magnetic resonance imaging (MRI) revealed bilateral oval cystic lesions lateral to the condylar capsule, whereas computed tomography (CT) apparently did not show the right hand side lesion. The cyst on the left side was surgically excised, and fine needle aspiration was performed on the right hand cyst. After 24 months, the long term follow-up showed no sign of recurrence.

Both synovial cysts and synovial chondromatoses originate from synovial tissue, and only one case has been reported to occur simultaneously in a patient. Our patient presented with a swelling of the right preauricular area and pain on opening the mouth. Magnetic resonance images demonstrated two cystic structures in the superficial lobe of right parotid gland. Under the clinical impression of a cyst in the salivary gland, an enucleation was performed. However, the final diagnosis based on microscopic examination was a synovial cyst associated with the right temporomandibular joint and a synovial chondromatosis arising within the cystic wall. Awareness of this combined lesion will help make a diagnosis and establish a proper treatment plan.